Bicycle and motorcycle or tricycle brakes are known in which the brake is mounted at the top of the wheel fork and is provided with a cable connected to a lever actuated by the operator on the handlebars of the cycle. Such caliper brakes are generally of one of two types.
For example, there are so-called "lateral-draw" caliper brakes in which a pair of arms are swingable about a common axis and are urged apart by a spring resting against a bridge piece also disposed along this axis. There also have been proposed so-called "central-draw" caliper brakes in which each of the arms is pivotally mounted upon a respective axis carried by an arcuate or stirrup-shaped bridge piece and generally urged outwardly by a respective spring disposed along the respective axis.
In both types of brakes the actuator is a cable which, in the lateral-draw system, has its Bowden sheath acting on one of the arms while the cable core is connected to the other. In the central-draw brake, the cable is connected to both of the arms and the sheath is fixed to the bicycle frame or the bridge piece.
A lateral-draw caliper brake of the type generally described above comprises two arms of different form, namely an arcuate arm and a Y-shaped arm. The two arms are mounted on a common axis disposed in the median plane of the wheel. This axis is fixedly defined by the bridge piece which supports the spring tending to spread the two jaws of the brake. The central-draw brake comprises a pair of symmetrical arms, each of which is pivotal about a respective axis disposed to one side of the median plane of the wheel. The bridge piece, in this embodiment, carries the two axes and enables the brake to be affixed to the top of the fork of the bicycle wheel.
The mounting of the arms on their respective axes is generally carried out with relatively complex means and consequently the mounting assemblies are relatively expensive and heavy. For purposes of illustration, it should be noted that the conventional technique to pivot an arm on a supporting member is to provide the arm with a throughgoing bore of a diameter sufficient to enable it to clear the diameter of a bolt which is locked to the fork of the wheel with a nut-and-counternut arrangement. For example, in the case of a lateral-draw brake, the bridge piece may constitute the bolt and may be extended by a shank which is threaded and passed with clearance through a bore in the pivotal arms. The arms are thus mounted for free rotation on a smooth part of the shaft formed by the bolt. Translatory movement of the arms is prevented by a nut and another nut may be provided as a counternut to lock the assembly in place.
A washer between the arms prevents frictional engagement of their juxtaposed faces during pivotal movement. The assembly must be made with considerable precision to avoid axial movement of the relatively pivotable parts to provide the rigidity required for effective braking action.
In the case of central-draw caliper brakes, a similar bolt, having a smooth portion along its length, serves as the pivot axis for each of the respective arms.